Gas pressure damper means for a circuit breaker mechanism

ABSTRACT

A piston operating in a cylinder is driven by gas pressure to one or the other of two end positions corresponding respectively to open and closed conditions of a circuit breaker. Oppositely projecting reduced area portions of the piston project into recesses at either end of the stroke to trap gas ahead of these portions to retard and substantially to stop the piston at each end of its stroke as it reaches stops delineating such ends of the strokes. A check valve is associated with each recess to allow the stop motion and prevent rebound and the relief pressure of each valve is varied in accord with pressure fluctuations in the driving gas supply so that the retarding and stop motion effects are adjusted to the piston speed as affected by the driving gas pressure.

United States Patent Houben [54] GAS PRESSURE DAMPER MEANS FOR A CIRCUIT BREAKER MECHANISM [30] Foreign Application Priority Data Mar. 14, 1969 Netherlands ..69.03953 [1.5. CI ..200/166 I-I, 200/34 R Int. Cl. ..H0lh 1/50 Field 01 Search ..200/166 H, 82 R, 148 A, 34 R;

[56] References Cited UNITED STATES PATENTS Geiger, Jr. ..200/34 X Forwald ..200/34 X 1151 3,655,935 1451 Apr. 11, 1972 3,253,107 5/1966 Gisiger ..200/148 A 3,267,231 8/1966 Douglas ..200/82 R 2,842,680 7/1958 Cromwell et al ..200/34 X 2,753,424 7/1956 Peek ..200/34 X Primary Examiner-H. 0. Jones Attorney-Snyder and Butrum [5 7] ABSTRACT A piston operating in a cylinder is driven by gas pressure to one or the other of two end positions corresponding respectively to open and closed conditions of a circuit breaker. Oppositely projecting reduced area portions of the piston project into recesses at either end of the stroke to trap gas ahead of these portions to retard and substantially to stop the piston at each end of its stroke as it reaches stops delineating such ends of the strokes. A check valve is associated with each recess to allow the stop motion and prevent rebound and the relief pressure of each valve is varied in accord with pressure fluctuations in the driving gas supply so that the retarding and stop motion effects are adjusted to the piston speed as affected by the driving gas pressure.

8 Claims, 4 Drawing Figures Patented April 11, 1972 3,655,935

FIG]

ATTORNEY GAS PRESSURE DAMPER MEANS FOR A CIRCUIT BREAKER MECHANISM The invention relates to an apparatus, such as an electric switch for high voltage, comprising a movable member, e.g. the movable switching contact with accessories of such a switch, said member being adapted to move between two end positions defined by stops, and a gas damper adapted to damp the movement of said movable member on the approach of a stop, said gas damper being provided with a cylinder and a piston, said cylinder and piston cooperating at least, when said movable member and the relevant stop approach each other, and confining a closed cylinder space having a volume, which decreases during the further movement of said member towards said stop, and containing a gas mass, which counteracts said further movement.

In apparatuses of this kind the gas damper has the task to reduce the great speed of the movable member to a harmless value before said member hits the stop. The kinetic energy of the movable member must be converted into other forms of energy which can be easily dissipated. To this object it has already been proposed to connect the cylinder space of the gas damper to a leak-off passage, through which a part of the gas mass contained in said space is forced, when the pressure in said space rises. A portion of the kinetic energy to be absorbed is then necessary for the transport of gas through said passage. An other portion of said energy is converted by the adiabatic compression of the gas contained in the damper into heat which can be given off to the surroundings.

Although in many cases both possibilities of converting energy suffice for the required braking action on the movable member of the apparatus, occasions can arise, in which it is impossible to obtain a reasonable result by the use of a leakoff passage and a good dissapation of heat. For instance, such an occasion presents itself in gas blast circuit breakers, in which sulphur hexafluoride (SF gas) is used to drive and to brake the movable switching contact and to extinguish the switching arc. In such circuit breakers the speed of the switching contact must be great, but the stroke of the damper may only be short, whereas it must be avoided that the switching contact is rebounded, as by a spring, by the strongly compressed gas contained in the damper. Especially, when SF gas is used, the danger of rebounding is great, since for that gas the ratio C,,/C,, is not much greater than 1, viz. 1.06 only, so that the rise of temperature will be small, when the gas contained in the damper is adiabatically compressed, and little kinetic energy can be converted into heat.

The invention has the object to provide an apparatus comprising a gas damper of the kind referred to, in which all requirements imposed on the gas damper can be satisfied in a simple manner. The invention consists in that the cylinder space of the gas damper is connected to the atmosphere or a low-pressure space by a passage provided with a loaded check valve which closes towards said cylinder space. If therein the pressure in the cylinder space of the gas damper exceeds a given value, after the gas damper has become effective, the check valve is pushed open and a portion of the compressed gas is discharged from said space. The result thereof is, that the gas pressure in said cylinder space suddenly falls so much that the gas left in said space is not able any more to push the movable member of the apparatus back against the driving force exerted thereon. If the cylinder and the piston of the damper are correctly dimensioned and the load of the check valve is correctly adjusted it is possible to reduce the speed of the movable member of the apparatus considerably over a short braking distance and thereupon to reduce the pressure in the damper so much by opening the check valve, that said movable member arrives at the stop with a speed which is practically reduced to zero.

The check valve may be loaded by a spring which, if required, is adjustable. In many occasions it is also possible to use to that end a gas cushion. If the apparatus is provided with a pneumatically driven movable member and if the driving pressure and the pressure of the gas contained in the damping cylinder, before the gas damper becomes effective, are, in normal operation, liable to vary within a given range, as happens in gas blast circuit breakers, in which the extinguishing gas is also used for driving and damping purposes, it is recommended to connect the space, in which the gas cushion loading the check valve is contained, to the high-pressure side of the pneumatic driving system. The load of the check valve, that means the effect of the gas damper, is then automatically adapted to the driving force, exerted on the movable member, e.g. the movable switching contact of the apparatus and also the kinetic energy thereof which has to be dissipated.

The invention also relates to the individual gas damper comprising a cylinder and a piston, which during operation confine a gas filled closed cylinder space, to which a passage provided with a loaded check valve closing towards said cylinder space and used to connect said space with the atmosphere or a lowpressure space is connected. Such a gas damper is suitable for use in existing apparatusses.

The invention will be further elucidated with the aid of the accompanying drawing. In the drawing FIG. 1 is an axial sectional view of a pneumatic driving mechanism for the movable switching contact of an electric switch provided with gas dampers according to the invention,

FIG. 2 is an axial sectional view of a first variant of the gas damper shown in FIG. 1,

FIG. 3 is an axial sectional view of a second variant of said gas damper, and

FIG. 4 is an axial sectional view of a third variant of said gas damper.

In FIG. 1 a cylinder is designated by l and a piston by 2. Said cylinder and said piston constitute together a pneumatic driving mechanism for a switching contact (not shown) of an electric switch which is coupled with the piston rod 3. The cylinder cover 4, 5 are provided with damping cylinder spaces 8, 9 which are open towards the spaces 6, 7 of the cylinder 1 and into which damping pistons 10, 11 formed on the piston 2 are forced, when the piston 2 approaches the stop 12 or the stop 13 for limitting its stroke. The damping cylinder spaces 8, 9 are each connected by a passage 14, 15 provided with a check valve l8, 19 closing towards said spaces and loaded by a spring l6, 17 to a space 20, 21 which communicates through ports 22, 23 with the atmosphere. Furthermore, the main cylinder spaces 6, 7 and the damping cylinder spaces 8, 9 are connected by passages 24, 25 and 26, 27 to multiple-way valves 28, 29 which are adapted to connect the main cylinder spaces 6, 7 either with the atmosphere or with a store vessel 30 containing gas under high pressure. Said multiple-way valves are also adapted either to close the damping cyl nder spaces or to connect same with said store vessel 30.

In the position shown in the drawing the switch is in its closed position, the main cylinder space 7 and the damping cylinder space 9 are connected with the high-pressure vessel 30 through the passages 25 and 27 and the valve 29 and the main cylinder space 6 communicates with the atmosphere through the passage 24 and the valve 28, whereas the damping cylinder space 8 is closed.

If the switch has to be opened, the coupled valves 28, 29 are rotated through an angle of 60,so that the main cylinder space 6 and the damping cylinder space 8 are connected with the vessel 30 and the main cylinder space 7 and the damping cylinder space 9 are brought into communication with the atmosphere, whereas the passage 27 connected to the damping cylinder space 9 is closed. The pistons 2, 10, 11 and the switching contact coupled therewith by the piston rod 3 are then moved upwards with great force and accelerated, till the damping piston l l is forced into the cylinder space 9 and compresses the gas contained therein. Due to this compression such a braking force is exerted on the moving members 2, 3, l0, 11 that their speed is practically reduced to zero. To that end the pressure of the gas contained in the space 9 will have to rise to a value which generally will be considerably higher than that exerting on the damping piston 11 a force which is equal to the force exerted on the piston 2 by the pressure of the gas contained in the vessel 30. When said high pressure value is reached the check valve 19 is pushed open, so that gas is discharged from the space 9 to the outside and the pressure in said space is suddenly considerably reduced. If care is taken that, before the check valve 19 has become closed again, the pressure in the space 9 is reduced to a valve, at which the driving force is only a little bit greater than the remaining braking force, the piston 2 will hit the stop 13 with low speed.

To allow the springs 16, 17 of the check valve 18, 19 to be adjusted, said springs rest against screwed plugs 31, 32.

It will be obvious, that the switching-in movement is braked by the damper 8, and the check valve 18 in the same way, when the piston 2 approaches the stop 12.

In the embodiment shown in FIG. 2 the screwed plug 32 is replaced by a piston 33 which is mounted for movement in a cylinder 34, the active space 35 of which contains gas under predetermined pressure. The gas pressure can be adjusted to the required value by means of the conduit 36 and the valve 37. However, the conduit 36 may also be connected to the vessel 30. In that case the valve 37 may be omitted and the gas pressure in the cylinder space 35 will adapt itself automatically to the driving force, that means to the kinetic energy of the movable member 2, 3, 10, ll of the apparatus. It is observed, that in this embodiment the spring 17 may be replaced by a rigid element.

In the variant shown in FIG. 3 the piston 33 of the embodiment shown in FIG. 2 is replaced by a diaphragm 38 which is connected to the check valve 40 by a rod 39. In FIG. 4 there is provided a bellows 41 instead of said diaphragm 38.

What I claim is:

1. In a circuit breaker apparatus having a movable member operable between opposite end positions for actuating a movable switching contact between closed and open conditions, means for driving said movable member including a supply of pressurized gas and a member driven thereby so that the speed of said movable member is in accord with the pressure of id supply, and at least one stop for limiting one of the end positions of said movable member, the improvement which comprises:

means associated with said movable member for exerting a retarding force on said movable member by compressing a mass of gas as said movable member approaches said one end position and including a damping space within which said mass of gas is compressed;

check valve means communicating with said damping space for permitting controlled escape of gas from said damping space whereby to control the retarding force exerted on said movable member as said stop is approached; and means connected to said check valve means for varying said controlled escape of gas in accord with the gas pressure of said supply, whereby to modify said retarding force in accord with the speed of said movable member.

2. In a circuit breaker apparatus as defined in claim 1 wherein said means associated with said movable member comprises a fixed cylinder having a portion defining said damping space and a piston operated by said movable member and movable within said damping space when said movable member approaches said one end position.

3. In a circuit breaker apparatus as defined in claim 2 wherein said piston is outside the confines of said damping space when said movable member is in its other end position and enters same only as said movable member approaches said one end position.

4. In the circuit breaker apparatus as defined in claim 3 including valve means for connecting said damping space with said supply to urge said movable member toward said other end position.

5. In a circuit breaker apparatus having a movable member operable between opposite end positions for actuating a movable switching contact between closed and open conditions, the improvement which comprises:

a cylinder having opposite end wall portions, at least one of which is provided with a dampin cylinder space;

a piston connected to said mova le member, said piston having an enlarged piston portion slidable in said cylinder and a reduced area piston portion aligned with but normally spaced from said damping cylinder space when said movable member is in one position thereof;

a source of pressurized gas;

means for introducing said pressurized gas into said cylinder and against said enlarged piston portion on that side of said piston opposite said damping cylinder space whereby to drive said movable member toward the other end position thereof and to trap a mass of gas ahead of said reduced area piston portion as said movable member approaches said other end position;

check valve means for venting said damping cylinder space at a pressure substantially higher than the pressure of said supply so as to allow said trapped mass of gas acting against said reduced area piston portion to reduce the velocity of said movable member substantially to zero as same reaches said other position thereof; and

means for introducing said pressurized gas into said damping cylinder space and into said cylinder on the same side of said piston as said damping cylinder space so as to return said movable member to said one position thereof.

6. In a circuit breaker apparatus as defined in claim 5 wherein the other end wall of said cylinder is also provided with a damping cylinder space and said piston includes a second reduced area portion aligned with the damping cylinder space in said other end wall; and check valve means associated with the damping cylinder space in said other end wall for venting such damping cylinder space at a pressure substantially greater than the pressure of said supply to reduce the velocity of said movable member substantially to zero as same reaches said one position thereof on the return of said movable member.

7. In a circuit breaker as defined in claim 6 including means associated with each check valve means for varying the pressure at which each damping cylinder space is vented according to the pressure of said supply.

8. In a circuit breaker as defined in claim 5 including means for varying the pressure at which said damping cylinder space is vented in accord with the pressure of said supply. 

1. In a circuit breaker apparatus having a movable member operable between opposite end positions for actuating a movable switching contact between closed and open conditions, means for driving said movable member including a supply of pressurized gas and a member driven thereby so that the speed of said movable member is in accord with the pressure of id supply, and at least one stop for limiting one of the end Positions of said movable member, the improvement which comprises: means associated with said movable member for exerting a retarding force on said movable member by compressing a mass of gas as said movable member approaches said one end position and including a damping space within which said mass of gas is compressed; check valve means communicating with said damping space for permitting controlled escape of gas from said damping space whereby to control the retarding force exerted on said movable member as said stop is approached; and means connected to said check valve means for varying said controlled escape of gas in accord with the gas pressure of said supply, whereby to modify said retarding force in accord with the speed of said movable member.
 2. In a circuit breaker apparatus as defined in claim 1 wherein said means associated with said movable member comprises a fixed cylinder having a portion defining said damping space and a piston operated by said movable member and movable within said damping space when said movable member approaches said one end position.
 3. In a circuit breaker apparatus as defined in claim 2 wherein said piston is outside the confines of said damping space when said movable member is in its other end position and enters same only as said movable member approaches said one end position.
 4. In the circuit breaker apparatus as defined in claim 3 including valve means for connecting said damping space with said supply to urge said movable member toward said other end position.
 5. In a circuit breaker apparatus having a movable member operable between opposite end positions for actuating a movable switching contact between closed and open conditions, the improvement which comprises: a cylinder having opposite end wall portions, at least one of which is provided with a damping cylinder space; a piston connected to said movable member, said piston having an enlarged piston portion slidable in said cylinder and a reduced area piston portion aligned with but normally spaced from said damping cylinder space when said movable member is in one position thereof; a source of pressurized gas; means for introducing said pressurized gas into said cylinder and against said enlarged piston portion on that side of said piston opposite said damping cylinder space whereby to drive said movable member toward the other end position thereof and to trap a mass of gas ahead of said reduced area piston portion as said movable member approaches said other end position; check valve means for venting said damping cylinder space at a pressure substantially higher than the pressure of said supply so as to allow said trapped mass of gas acting against said reduced area piston portion to reduce the velocity of said movable member substantially to zero as same reaches said other position thereof; and means for introducing said pressurized gas into said damping cylinder space and into said cylinder on the same side of said piston as said damping cylinder space so as to return said movable member to said one position thereof.
 6. In a circuit breaker apparatus as defined in claim 5 wherein the other end wall of said cylinder is also provided with a damping cylinder space and said piston includes a second reduced area portion aligned with the damping cylinder space in said other end wall; and check valve means associated with the damping cylinder space in said other end wall for venting such damping cylinder space at a pressure substantially greater than the pressure of said supply to reduce the velocity of said movable member substantially to zero as same reaches said one position thereof on the return of said movable member.
 7. In a circuit breaker as defined in claim 6 including means associated with each check valve means for varying the pressure at which each damping cylinder space is vented according to the pressure of said supply.
 8. In a circuit breaker as defined in claim 5 incLuding means for varying the pressure at which said damping cylinder space is vented in accord with the pressure of said supply. 